The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 2001-219320, filed Jul. 19, 2001, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to the arrangement of a balancer of an engine for a planing boat, and more particularly to the arrangement of a balancer for a small-sized planing boat.
2. Description of Background Art
Several types of engines with balancers are known. They include an engine provided with balancers (so-called xe2x80x9cbiaxial balancersxe2x80x9d) which rotate in reverse directions, an engine with balancers arranged under a crankshaft, and an engine with balancers arranged on both sides of a cylinder-over a crankshaft.
When balancers are arranged under the crankshaft, the engine height is high, and tile engine is not suited for mounting in a small-sized planing boat. This configuration also presents a problem in that the center of the gravity is high. Furthermore, the position of the crankshaft is relatively high, because the balancers are arranged under the crankshaft. As a result, is difficult to couple the shaft of a jet propulsion pump on a line extending from the crankshaft.
Similarly, in an engine with balancers arranged on both sides of the cylinder over the crankshaft, the degree of freedom in arranging accessories is limited.
It is an object of the present invention is to solve these problems by providing an engine having a balancer suitable for mounting in a small-sized planing boat, while at the same time maintaining a low center of gravity of the boat and allowing a greater degree of freedom in the placement of boat accessories.
To achieve the objects, the engine of the present invention is mounted in the boat surrounded by the hull and the deck. The engine includes an upper case and a lower case, respectively divided on a parting face parallel to the crankshaft, and a balancer arranged on the left and on the right of the crankshaft on the parting face.
A balancer driving gear is provided at the periphery of a one-way clutch for starting the engine, the clutch being located at the back of an ACG rotor disposed at the end of the crankshaft.
An oil tank is provided at the front of the engine in the direction of an extended line from the crankshaft, and an oil supply passage to a balancer support is formed in an oil tank case. Further, a restrictor is provided in the oil supply passage. In addition, the oil tank covers a chamber for driving the ACG rotor, the balancer, and the starter motor.
Another aspect of the present invention includes arranging the starter motor of the engine and the balancer in parallel, and arranging the idle gear of one balancer on the side opposite to the starter motor, with the crankshaft between them. Further, the starter motor of the engine and the balancer are arranged in parallel, and the idle gear of one balancer is arranged on the side opposite to the starter motor, with the cylinder of the engine between them.
The actions and effects of the present invention are summarized below.
Since the engine for the small-sized planing boat is provided with the upper case and the lower case, respectively divided on the parting face parallel to the crankshaft, and the balancer is arranged on the left and on the right of the crankshaft on the parting face, the overall height of the engine can be reduced.
Therefore, the engine is suitable for mounting in the small-sized planing boat having only small space in the body. Simultaneously, the center of the gravity of the boat can be lowered.
Also, the position of the crankshaft can be lowered, with the result that the balancer is arranged on the left and on the right of the crankshaft on the face for parting the upper case and the lower case divided on the parting face parallel to the crankshaft. Further, the shaft of the jet propulsion pump can be coupled on the extended line of the crankshaft.
Furthermore, since the balancer is arranged on the left and on the right of the crankshaft on the parting face, a degree of freedom of arranging accessories can be achieved. As such, the engine is suitable for mounting in a small-sized planing boat, and simultaneously, the center of the gravity of the boat can be lowered.
In addition, even though the oil pan under the engine is small-sized, the agitation of oil by the balancer can be inhibited, compared with the conventional engine having the balancer provided under the crankshaft. Since the oil pan is small, the overall height of the engine can be lowered further.
Since the balancer driving gear is provided close to the back of the ACG rotor, which is disposed at the end of the crankshaft, a driving system of the balancer can be miniaturized, and the overall length of the engine can be reduced.
Since the one-way clutch for starting the engine is provided at the back of the ACG rotor, and the balancer driving gear is provided to the periphery of the one-way clutch, the overall length of the engine can be further reduced by the amount by which the one-way clutch of a starting system and the balancer driving gear overlap.
Since the oil tank is provided at the front of the engine in the direction of the extended line from the crankshaft and the oil supply passage to the balancer support is formed in the case of the oil tank, the whole engine can be reduced in size, and piping for the oil supply passage to the balancer support is not required.
Since a restrictor is provided in the oil supply passage, air is easily separated by the restrictor even if the air is mixed into the oil as it passes toward the balancer support. Therefore, lubrication of the balancer shaft is adequately provided.
Since the oil tank covers the chamber for driving the ACG rotor, the balancer and the starter motor, a separate cover is not required, and the overall length of the engine can be further reduced. In addition, noise can be reduced by the sound absorption effects of oil in the oil tank.
Since the starter motor of the engine and the balancer are arranged in parallel and the idle gear of one balancer is arranged on the side opposite to the starter motor with the crankshaft between them, the starter motor and the balancer driving system can be arranged compactly around the crankshaft. As a result, the center of the gravity of the engine can be lowered, and the center of the gravity of the whole boat can also be lowered.
Since the starter motor of the engine and the balancer are arranged in parallel and the idle gear of one balancer is arranged on the side reverse to the starter motor with the cylinder of the engine between them, the starter motor and the balancer driving system can be arranged compactly near the longitudinal axis of the engine. Therefore, the weight of the engine, including the starter motor and the driving system, can be centralized near the center of the boat, and the turning performance of the boat can be enhanced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.